I think twice I week should be ok. If you are in any discomfort for a serious amount of time, def consult a doctor about it. They will know better than us. Two stories for you:

An Irish Judoka who helped set up Judo club in a Scottish University and had a very successful time in tournaments throughout the 90's, winning many competitions, had to knock Judo on the head as he had bad Arthritis by the time he was 38. Now I don't know for sure that it was Judo, but this guy was competing incessantly, and am sure it didn't help him.

Walter, guy who ran my old Judo club, won gold in the World Judo Masters last year. He ws 61 years old. Still hits the Masters squad session every week, fit as a fiddle.

Now what does all this tell you?? Not much really! I knew of someone who did a lot of competition until he couldn't do Judo anymore. I have seen a man who is near retiring age and can is still as strong as an Ox, and fitter than men half his age.

There are many Judoka who do Judo for a long long time with no hand problems. No reason why you shouldn't be able to either.

When you go down to the class, ask someone to show you how to tape your fingertips. Common practice is this, even amongest Olympian Judokas. This will stop any nastys like getting fingernails ripped out on someones gi as they violently try to pull free of your grip lol!

I did Judo for 35 years with no appreciable effects on my hands... if that means anything. I also disintegrated one of my knuckles doing karate with no particular hampering of my movement. I think it's individual with everyone.

I have osteoarthritis in my hip now, but I don't attribute that to Judo, but to lack of exercise while my wife was sick. Most problems from martial arts training come from injuries, not "repeated stress" injury or conditions. 45 years of training, and I have the hands and wrists of a piano player or violinist... and I train 3 times a week.

FWIW

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What man is a man that does not make the world a better place?... from "Kingdom of Heaven"

Actually, I think that judo might enhance your abilities as a massage therapist. I did judo for 6 years as a kid and one of the things judo did for me was to give me an iron grip (which I would guess might enhance one's massage skills). Judo tends to more likely cause shoulder and/or knee injuries rather than hand injuries. FWIW even though I left judo many years ago (due to a rib injury) I still think it's the greatest sport in the world!!

I don't think there's much long term risk of injury and it might even be beneficial as Tom pointed out. However, short term injuries can be quite a pain sometimes- I have sprained my thumb and little finger and have had a number of small cuts on the fingers since I started Judo. The solution to this is to use tape liberally, some people even tape 2 fingers together. I don't tape my fingers personally, but then my career doesn't depend on their working order.

Well I've injured my fingers here and there over the years, much of it from gripping gi's and getting twisted etc...I actually am in school currently for massage, and I will tell you that it may aggravate old injuries, but so far that is easy to take care of with stretching etc.

I am not a Judoka so I can't give a real answer, but personally I doubt you have much to be worried about.

Your hands will (probably) feel pretty fatigued when you start massage school regardless, but I will say that martial arts training has generally given me a condition advantage over other people doing massage, so yeah while it may give you a few minor injuries, it could quite possibly have a positive effect overall.